SafeDisk - RSC stream cipher

RSC stream cipher

RSC - stream cipher with a key length of 216 bits. As against the majority of other stream ciphers processs data by units till 32 bits.

On the diagram scheme of algorithm at the left is figured the block. A and B - 32 bit constants depending on a key. F - converted nonlinear function also depending on a key. IV - initial vector. Formally one step of algorithm can be described so:

On each step the new value IV is calculated which there is not that other, as an internal state of algorithm.

The algorithm of function evaluation F is figured on the right. Here ROR (x, n) - circular shift 32-bits word x to the right on n bit. CountOfBits(x) - function defining an amount bit in a word x nonzero. S - array of shifts generated from a key.

Despite of a relative simplicity, the algorithm behaves well enough first of all because of strong nonlinearity function F. In applications such as SafeDisk it is not required to the special stability of algorithm to plain-text attack. It has allowed considerably to simplify step of encoding and to receive maximum speed.

For more detailed acquaintance you can download implementation RSC stream cipher on ANSI C.

The cipher RSC can be used without what or license limitations for any purposes. The reference to authorship SoftLab is mandatory.